RFC 7187

Internet Engineering Task Force (IETF) C. Dearlove
Request for Comments: 7187 BAE Systems ATC
Updates: 7181 T. Clausen
Category: Standards Track LIX, Ecole Polytechnique
ISSN: 2070-1721 April 2014 Routing Multipoint Relay Optimization for
the Optimized Link State Routing Protocol Version 2 (OLSRv2)
Abstract
This specification updates the Optimized Link State Routing Protocol
version 2 (OLSRv2) with an optimization to improve the selection of
routing multipoint relays. The optimization retains full
interoperability between implementations of OLSRv2 with and without
this optimization.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7187.
Copyright Notice
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include it. However, inclusion of this optimization is advised; it
can, in some cases, create smaller and fewer messages, without ever
having the opposite effect.
[RFC7181] defines the properties for the selection of routing MPRs
from among a router's symmetric 1-hop neighbors. The properties are
o the selected MPRs must consist of a set of symmetric 1-hop
neighbors that cover all the symmetric 2-hop neighbors, and
o the selected MPRs must do so retaining a minimum distance route
(1-hop, if present, or 2-hop) to each symmetric 2-hop neighbor.
The discussion in the latter part of Section 6.2 of [RFC7185]
indicates that this requirement is overly prescriptive for routing
MPR selection. The update to [RFC7181] described in this
specification permits a router to use the described optimization,
while still being considered compliant with OLSRv2.
Note that whether or not a router is considered compliant, a router
that implements the optimization described in this specification will
interoperate successfully with routers that are not implementing this
optimization.
4. Routing MPR Selection
A set of routing MPRs created as specified in [RFC7181] MAY be
optimized in the following manner. Note that this uses the notation
of Section 18.2 of [RFC7181]:
1. If there is a sequence x_0, ..., x_n of elements of N1 such that:
* x_0 is a routing MPR,
* x_1, ... , x_n have corresponding elements y_1, ..., y_n of
N2, and
* d1(x_0) + d2(x_0,y_1) + ... + d2(x_m-1,y_m) < d1(x_m) for m =
1, ... , n,
then x_1 to x_n may be removed from the set of routing MPRs, if
selected.
Note that "corresponding elements" in N1 and N2 means that these
elements represent the same router. All of this information is
available from information gathered by NHDP [RFC6130].

5. Security Considerations
The update to OLSRv2 [RFC7181] does not introduce any new protocol
signals, nor does it change the processing of any received protocol
signals.
This update to OLSRv2 [RFC7181] permits an implementation that is
compliant with OLSRv2 to (potentially) eliminate some unneeded
routers from the routing MPR sets generated as described in
[RFC7181], which also eliminates the need to include the
corresponding information in generated Topology Control (TC)
messages. Because this information is not used when included, this
update to OLSRv2 [RFC7181] does not present any additional security
considerations, beyond those described in [RFC7181].
6. Acknowledgments
The authors would like to gratefully acknowledge Philippe Jacquet
(Alcatel-Lucent) for intense technical discussions and comments.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6130] Clausen, T., Dean, J., and C. Dearlove, "Mobile Ad Hoc
Network (MANET) Neighborhood Discovery Protocol (NHDP)",
RFC 6130, April 2011.
[RFC7181] Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
"The Optimized Link State Routing Protocol Version 2", RFC
7181, April 2014.
7.2. Informative References
[RFC2501] Macker, J. and S. Corson, "Mobile Ad hoc Networking
(MANET): Routing Protocol Performance Issues and
Evaluation Considerations", RFC 2501, January 1999.
[RFC3626] Clausen, T. and P. Jacquet, "The Optimized Link State
Routing Protocol", RFC 3626, October 2003.
[RFC7185] Clausen, T., Dearlove, C., and P. Jacquet, "Rationale for
the Use of Link Metrics in the Optimized Link State
Routing Protocol Version 2 (OLSRv2)", RFC 7185, April
2014.